Fabrication of La2O3 Uniformly Doped Mo Nanopowders by Solution Combustion Synthesis Followed by Reduction under Hydrogen

This work reports the preparation of La2O3 uniformly doped Mo nanopowders with the particle sizes of 40-70 nm by solution combustion synthesis and subsequent hydrogen reduction (SCSHR). To reach this aim, the foam-like MoO2 precursors (20-40 nm in size) with different amounts of La2O3 were first synthesized by a solution combustion synthesis method. Next, these precursors were used to prepare La2O3 doped Mo nanopowders through hydrogen reduction. Thus, the content of La2O3 used for doping can be accurately controlled via the SCSHR route to obtain the desired loading degree. The successful doping of La2O3 into Mo nanopowders with uniform distribution were proved by X-ray photon spectroscopy and transmission electron microscopy. The preservation of the original morphology and size of the MoO2 precursor by the La2O3 doped Mo nanopowders was attributed to the pseudomorphic transport mechanism occurring at 600 degrees C. As shown by X-ray diffraction, the formation of Mo2C impurity, which usually occurs in the direct H-2 reduction process, can be avoided by using the Ar calcination-H-2 reduction process, when residual carbon is removed by the carbothermal reaction during Ar calcination at 500 degrees C.